Idiosyncrasies of scalp melanoma

Objectives/Hypothesis: Examine the accuracy of sentinel lymph node biopsy (SNB) in scalp melanoma (SM), patterns of nodal metastases, patient outcomes, and the utility of immunohistochemistry (IHC) in SNB evaluation. Study Design: Retrospective. Methods: There were 22 patients, 4 females and 18 males. Sentinel lymph nodes (SLN) were localized via preoperative lymphoscintigraphy, intraoperative gamma probe, and Lymphazurin injection. SLNs were stained with hematoxylin-eosin, S-100, HMB-45, Melan-A, micropthalmia transcription factor, and tyrosinase. SLNs were grouped into cervical (levels 1-5) and extracervical (parotid, suboccipital, retroauricular) regions. Results: There were 13 posterior and 9 anterior SMs. The first SNB were mapped to the extracervical regions in 77% of posterior and 78% of anterior lesions. SLN number ranged from 1 to 5. Ten patients had positive SLNs (PSLN). Forty percent of the PSLN group had SLNs mapped in both cervical and extracervical sites. Six underwent completion lymphadenectomy, with no additional positive nodes identified. No significant difference between PSLN and negative sentinel node (NSLN) patients was seen when compared by SLN number, Breslow's thickness, tumor ulceration, and clinical outcomes. Mean follow-up was 35 months. One patient died of disease. One isolated regional recurrence occurred. Sixty percent of PSLN and 92% of NSLN patients were recurrence free at last follow-up. One distant metastasis occurred in the NSLN group, and one local, one regional, and two patients with distant metastases were in the PSLN group at the time of last follow-up. Additional IHC did not detect other metastases in the NSLN group. Conclusions: SM is aggressive, as demonstrated by the high rate of SLN metastases, and there were no significant histopathologic factors in the primary tumor that predicted the presence of SLN metastases. SNB was accurate. The majority of first SLNs were localized in extracervical basins.